1. Technical Field
The present invention relates generally to a failure analysis system having a looped interface. Specifically, it relates to a failure analysis system in a looped interface that includes a controller and an enclosure service unit under a node device connected to the looped interface. The enclosure service unit accepts a command from the controller via the node device.
In one exemplary embodiment, the present invention relates to a failure analysis system in a looped interface having a doubled FC-AL (Fiber-channel Arbitrated Loop) that includes an enclosure service unit loading an ESI (Enclosure Service Interface) controller SES (SCSI Enclosure Service) connected to a respective loop system so that, even though failures occur in all loop systems, a loop failure analysis may be executed.
2. Related Art
Recently, an interface which connects node devices in a loop (e.g., a Fiber Channel Arbitrated Loop (FC-AL)) has been widely used in a node device system (e.g., disk array apparatuses) and the like, since it has a simple connecting configuration of cables and can easily accommodate device extensions. However, this type of interface has a problem in that, when signals cannot propagate in the loop because of failure or the like in the interface circuits of connected devices (this is called, for example, a loop abnormality or link down), the entire loop cannot be used. For example, even though a failure occurs in only one device, all devices connected to the loop cannot be used.
For this reason, these devices may include interface circuits for two ports (duplex) so that they are connected to two independent loops. With this configuration, even when one loop of the dual loop interfaces is out of use because of a failure or the like, accesses may be performed using the other loop, to thereby improve reliability. Further, this kind of disk array apparatus may include a function of identifying a faulty device and restoring the failure when a loop abnormality occurs, by detecting which device is faulty and isolating it from the loop.
For example, JP 2004-94774 A, describes a node device system (e.g., disk array apparatus) having a double FC-AL. If failures occur in both loop systems due to one of the disk failures, an enclosure service unit controls the disconnect/reconnect state of each disk array to automatically perform a single disconnection processing for all disks. Configuration and operation of the disk array apparatus in two conventional examples will be explained with reference to FIGS. 5 though 9.
Hereinbelow, loop A components labels are discussed as “Ax” and loop B components labels are discussed as “Bx”.
FIG. 5 is an exemplary block diagram showing an exemplary configuration of the conventional disk array apparatus in a normal state. For example, in this disk array apparatus, a host may directly access the enclosure service units (e.g., FC Direct Attached SES (SCSI Enclosure Service)). As shown in this figure, the disk array apparatus having a doubled FC-AL is connected, for example, plural disks 21-2N are connected to two loops A41, B42 (FC-AL A, FC-AL B), respectively, via loop connection switch units A31, B32.
In each loop system A, B, enclosure service units A51, B52 are installed respectively, being interconnected via path 130. For example, these enclosure service units A51, B52 contain loop connection control units A513, B523 that control disconnection and connection of each disk 21-2N from the loop system (FC-AL) and are connected to the aforementioned loop connection switch units A31, B32 via paths 514 and 524. In addition, in each loop system, disk control units A71, B72 generate a control command to enclosure service units A51 and B52 to perform disk control.
As shown in FIG. 6, a failure is assumed to occur in the FC-AL B loop system (one of the two loop systems) in the disk 24. In this case, since FC-AL A41 that is in the other loop system, is operated normally by disk control unit A71, from normal looped enclosure service unit A51 using path 130, it accesses looped (FC-AL B42) enclosure service unit B52 in FC-AL B loop system where the failure has occurred. Loop connection control unit B523 sequentially disconnects the disk 21-2N and uses path 524 to perform failure analysis. (See dotted arrow in FIG. 6).
Next, FIG. 7 shows an exemplary mode when a failure occurs in both loop systems in specified disk 24. As shown in this figure, if a failure occurs in both systems in disk 24 neither loop system (A, B) can be operated, so that access from disk control units 71, B72 to respective enclosure service units A51, B52 is completely disabled. Therefore, failure may not be analyzed without further treatment. For this reason, as shown in FIG. 8, in one conventional method, at this point, both loop systems A, B are then disconnected from each disk 21-2N so that disk control units A71, B72 may access the respective enclosure services units A51, B52.
As a result, each of enclosure service units A51, B52 can then sequentially connect to disk 21-2N to perform a failure analysis. In other words, if a re-connection command is sequentially given from the disk control units 71, 72 after recovering both loop systems, the disk 24 causing the loop failure may be identified so that the abnormal disk can be disconnected from the FC-AL to continue operation.